A system for triggering improvised explosive devices (IEDs) with an alternating magnetic field. In one embodiment, the magnetic field is produced by a magnetic field projector in the shape of one-half of a torus, the half-torus being composed of several conductive segments referred to as toroidal wedges. A poloidal current flows in each toroidal wedge, producing a magnetic field that is projected by the half-torus. The magnetic field may induce a current, producing heating, in a conductive loop in an IED and triggering the IED.
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1. A system for projecting an oscillatory magnetic field, the system comprising:
a plurality of conductive toroidal wedges;
each toroidal wedge being a section of tube having two substantially planar ends, at least one of the substantially planar ends having a normal oblique to the centerline of the tube,
the section of tube having a slit extending between the two substantially planar ends, and
a plurality of non-conductive spacers;
the toroidal wedges being assembled to form an assembly substantially in the shape of a portion of a torus.
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wherein:
the toroidal wedges of the plurality of toroidal wedges comprise a plurality of holes;
the non-conductive spacers of the plurality of non-conductive spacers comprise a plurality of holes; and
the upper non-conductive support plate and the lower non-conductive support plate comprise a plurality of holes located so as to be aligned with the holes in the toroidal wedges and the holes in the non-conductive spacers, and
each of the plurality of pins is positioned in a hole in the upper non-conductive support plate or in the lower non-conductive support plate, and in a hole in a toroidal wedge or in a non-conductive spacer.
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1. Field
One or more aspects of embodiments according to the present invention relate to a system for projecting a low-frequency oscillating magnetic field, and more particularly to an electromagnetic system for triggering improvised explosive devices (IEDs) using an alternating magnetic field.
2. Description of Related Art
Improvised explosive devices are explosive devices typically deployed against troops or civilians. An IED may be hidden under a roadway along which the intended targets are expected to travel, and triggered remotely, e.g., by an observer, or locally, e.g., by a pressure-sensitive switch which detects the presence of the targets.
IEDs triggered by pressure sensitive switches may be made harmless by triggering them with a vehicle pushing a heavy armored roller, or “mine roller” that may be driven ahead of troops on foot or ahead of other more vulnerable targets. If, however, an IED is designed to be remotely triggered, or remotely armed, after a mine roller has passed, the mine roller may fail to trigger it and it may remain a threat.
Thus, there is a need for a more reliable system for triggering IEDs.
In one embodiment, a system for triggering improvised explosive devices with an alternating magnetic field includes a magnetic field projector in the shape of one-half of a torus. The half-torus is composed of several conductive segments referred to as toroidal wedges. A poloidal current flows in each toroidal wedge, producing a magnetic field that is projected by the half-torus. The magnetic field may induce a current in a conductive loop in the IED, heating a bridge wire within the detonator of the IED to a sufficiently high temperature to trigger a detonator in the IED.
According to an embodiment of the present invention, there is provided a system for projecting an oscillatory magnetic field, the system including: a plurality of conductive toroidal wedges; each toroidal wedge being a section of tube having two substantially planar ends, at least one of the substantially planar ends having a normal oblique to the centerline of the tube, the section of tube having a slit extending between the two substantially planar ends, and a plurality of non-conductive spacers; the toroidal wedges being assembled to form an assembly substantially in the shape of a portion of a torus.
In one embodiment, the section of tube forming a toroidal wedge of the plurality of toroidal wedges has a cross section that is substantially circular.
In one embodiment, the section of tube forming a toroidal wedge of the plurality of toroidal wedges has a cross section that is substantially rectangular.
In one embodiment, the slit in the section of tube forming a toroidal wedge of the plurality of toroidal wedges is substantially parallel to the centerline of the section of tube.
In one embodiment, the slit in the section of tube forming a toroidal wedge of the plurality of toroidal wedges is substantially in a plane parallel to the normals of the substantially planar ends of the section of tube.
In one embodiment, the angle between the normals of the substantially planar ends of the section of tube forming a toroidal wedge of the plurality of toroidal wedges is less than 45 degrees.
In one embodiment, the angle between the normals of the substantially planar ends of the section of tube forming a toroidal wedge of the plurality of toroidal wedges is greater than 10 degrees.
In one embodiment, the minor diameter of the portion of the torus is greater than 4 inches and less than 8 inches.
In one embodiment, the major diameter of the portion of the torus is greater than 12 inches and less than 24 inches.
In one embodiment, the tube diameter of the portion of the torus is greater than 4 inches and less than 8 inches.
In one embodiment, the centerline length of the section of tube forming a toroidal wedge of the plurality of toroidal wedges is less than the tube diameter of the portion of the torus.
In one embodiment, the section of tube forming a toroidal wedge of the plurality of toroidal wedges includes a layer of steel and a layer of copper.
In one embodiment, the thickness of the layer of copper is less than 10% of the thickness of the layer of steel.
In one embodiment, the non-conductive spacers are composed primarily of fiberglass reinforced plastic.
In one embodiment, the system includes an upper non-conductive support plate and a lower non-conductive support plate, configured to sandwich the assembly.
In one embodiment, the system includes a plurality of pins, wherein: the toroidal wedges of the plurality of toroidal wedges include a plurality of holes; the non-conductive spacers of the plurality of non-conductive spacers include a plurality of holes; and the upper non-conductive support plate and the lower non-conductive support plate include a plurality of holes located so as to be aligned with the holes in the toroidal wedges and the holes in the non-conductive spacers, and each of the plurality of pins is positioned in a hole in the upper non-conductive support plate or in the lower non-conductive support plate, and in a hole in a toroidal wedge or in a non-conductive spacer.
In one embodiment, the system includes a plurality of conductive bridges, a conductive bridge of the plurality of conductive bridges connected to a first toroidal wedge and to a second toroidal wedge, the first toroidal wedge, the conductive bridge, and the second toroidal wedge being thereby connected in series.
In one embodiment, the system includes a class E amplifier configured to drive a current through a toroidal wedge.
In one embodiment the system is configured to project an oscillatory magnetic field oscillating at a frequency in the range from 1 megahertz to 30 megahertz.
Features, aspects, and embodiments are described in conjunction with the attached drawings, in which:
The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments of a multisegmented toroidal magnetic field projector provided in accordance with the present invention and is not intended to represent the only forms in which the present invention may be constructed or utilized. The description sets forth the features of the present invention in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and structures may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention. As denoted elsewhere herein, like element numbers are intended to indicate like elements or features.
In toroidal magnetic devices, such as tokamaks, toroidal inductors, and toroidal transformers, a poloidal current flows around the outer surface of a torus, generating a toroidal magnetic field inside the torus. If the torus is formed as a surface of revolution by rotating a circle around the Z-axis, then the toroidal direction is one that is at each point perpendicular to the Z-axis and to a line from the Z-axis to the point, and the poloidal direction is, everywhere on the surface of the torus, perpendicular to the toroidal direction, i.e., it is tangential to the circle. The poloidal current may be carried, for example, by turns of wire wound in the poloidal direction around the surface of the torus. The lines of magnetic field in such a configuration are circles in the toroidal direction. Referring to
In one embodiment, such a magnetic field is used to trigger an IED, for example, by inducing a current in a conductive loop in the IED, heating a bridge wire within the detonator of the IED to a sufficiently high temperature to trigger a detonator in the IED. The magnetic field is an alternating field with a frequency in the range of 1 MHz to 30 MHz. This magnetic field has a near-field component and a radiated component; the radiated component corresponds to electromagnetic waves that radiate from the torus, carrying electromagnetic energy away.
In an application in which the near-field component is used to trigger an IED, it may be advantageous for the near-field component of the magnetic field to be large compared to the radiated component. In
Referring to
In one embodiment, the toroidal wedges 310 are formed by cutting short, wedge-shaped pieces from a round conductive tube or pipe, e.g., copper pipe. The tube has a centerline, or “axis” that is parallel to the wall (or walls, for, e.g., a square tube) of the tube, and runs along the center of the tube. Each cut is substantially planar and oblique to the centerline of the tube, i.e., the normal vector, or “normal”, to the plane of the cut forms an angle, or “cut angle”, with the centerline of the tube. The length of the tube measured along its centerline, i.e., the distance between the two points at which the centerline intersects the two respective cutting planes, is referred to as the centerline length of the toroidal wedge. In one embodiment, a plane parallel to the normals to the planes of the two cuts is also parallel to the centerline of the tube, and the cut angles are equal, for the two ends of each of the toroidal wedges 310, so that when one of the toroidal wedges 310 is viewed from the side, from a direction perpendicular to both normals, it appears in profile as a trapezoid. In one embodiment, the wedges are shaped and positioned such that the linear separation between two adjacent wedges is constant. After each piece is cut from the tube, a slit 315 may be formed at a point on the circumference of the piece, to provide attachment points for current drive conductors, such as wires. The toroidal wedges formed in this manner may then be assembled into a shape approximating, with a number of short, straight segments, the shape of a half-torus. The major and minor diameters of the half-torus will depend on the length of each toroidal wedge 310 (both the major and minor diameters being greater if the length is greater) and on the cut angles (both the major and minor diameters being smaller if the cut angles are greater), and the number of toroidal wedges 310 used to form a half-torus will depend on the cut angles (the number of toroidal wedges 310 being smaller if the cut angles are greater). In one embodiment, the tube is not round but has a different cross section, being, e.g., square, rectangular, or hexagonal, and a shape substantially in the shape of a portion of a torus is formed with pieces of tubing having cross sections that are not round. As used herein, a “torus” may have a circular cross section as in the embodiment illustrated in
In another embodiment, a toroidal wedge 310 may be formed by rolling a flat piece of sheet metal, having two flat edges, and two edges each cut in the shape of a sinusoid, into a round shape so that the flat edges nearly meet.
Because the skin depth in copper at frequencies in the range between 1 MHz and 30 MHz is small, e.g., approximately 12 micrometers at 30 MHz, the toroidal wedge 310 may be composed of another material, e.g., steel, or a dielectric, with a thin coating of copper, which may be less than 10% of the thickness of the other material, and the toroidal wedge may nonetheless substantially maintain the electrical performance of a toroidal wedge composed of pure copper.
Referring to
In one embodiment, 10 toroidal wedges are used to form an assembly approximating, i.e., substantially in the shape of, a half-torus. Each cut of each toroidal wedge may have a cut angle of approximately 9 degrees, so that the angle between the normals of the substantially planar ends of each toroidal wedge is approximately 18 degrees. Round tube with a diameter of approximately 6 inches forms each toroidal wedge, and the half-torus has a minor diameter of 6 inches and a major diameter of 18 inches. In other embodiments, more or fewer toroidal wedges are used to form the assembly. In one embodiment, 4 toroidal wedges are used and the angle between the normals of the substantially planar ends of each toroidal wedge is approximately 45 degrees.
In one embodiment, a conductive bridge 360 connects each toroidal wedge 310 to the two adjacent toroidal wedges 310, or, for the toroidal wedges 310 on the ends of the half-torus, to the adjacent toroidal wedge 310. Each conductive bridge 360 connects the conductor on the lower side of the slit 315 of one wedge to the conductor on the upper side of the slit 315 on an the adjacent wedge, so that the toroidal wedges 310 are all wired in series. A 100 ampere (A) current driven through the series circuit then results in each toroidal wedge 310 carrying 100 A. A class E amplifier may be used to drive current through the toroidal wedges and the conductive bridges in series. In another embodiment, each toroidal wedge 310 is separately driven, e.g., by a class E amplifier connected to the two sides of the slit 315.
In one embodiment, driving a current of 100 A through each of the toroidal wedges 310 results in a projected magnetic field having a value of at least 70 A-turns/m (ampere-turns per meter) within most of a volume measuring 5.8 inches×25.5 inches×15 inches, and capable of, e.g., triggering an IED buried within a corresponding volume of ground assuming the conductivity of the ground is sufficiently low, and that 70 A/m is sufficient to trigger the IED.
Referring to
Referring to
Referring to
Although limited embodiments of a multisegmented toroidal magnetic field projector have been specifically described and illustrated herein, many modifications and variations will be apparent to those skilled in the art. For example, although the illustrated embodiments include toroidal wedges that are substantially identical, the toroidal wedges in an assembly may differ, being composed of different materials, for example. Accordingly, it is to be understood that the multisegmented toroidal magnetic field projector employed according to principles of this invention may be embodied other than as specifically described herein. The invention is also defined in the following claims, and equivalents thereof.
Crouch, David D., Kato, Keith G.
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Oct 02 2014 | CROUCH, DAVID D | Raytheon Company | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 034055 | /0212 | |
Oct 08 2014 | KATO, KEITH G | Raytheon Company | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 034055 | /0212 | |
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